ENH: dummy I/O for nullObject, additional null subclass for zero/one

- the zero::null and one::null sub-classes add an additional null
  output adapter.

  The function of the nil class (special-purpose class only used for
  HashSet) is now taken by zero::null.

applications/test/HashSet/Test-hashSet.C

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011 OpenFOAM Foundation
-     \\/     M anipulation  | Copyright (C) 2017 OpenCFD Ltd.
+     \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -26,6 +26,7 @@ Description
 \*---------------------------------------------------------------------------*/
 
 #include "hashedWordList.H"
+#include "nil.H"
 #include "HashSet.H"
 #include "Map.H"
 #include "labelPairHashes.H"
@@ -69,6 +70,8 @@ int main(int argc, char *argv[])
 
     Info<< "tableA keys: "; tableA.writeKeys(Info) << endl;
 
+    Info<< "tableB content: " << tableB << endl;
+
     auto keyIterPair = tableA.keys();
     for (const auto& i : keyIterPair)
     {

applications/test/sizeof/Test-sizeof.C

@@ -61,6 +61,10 @@ int main(int argc, char *argv[])
         nil x;
         cout<<"nil:" << sizeof(x) << nl;
     }
+    {
+        zero x;
+        cout<<"zero:" << sizeof(x) << nl;
+    }
     {
         bool x(0);
         cout<<"bool:" << sizeof(x) << nl;
@@ -93,6 +97,10 @@ int main(int argc, char *argv[])
         cout<<"double:" << sizeof(double) << nl;
     }
 
+    {
+        cout<<"string:" << sizeof(Foam::string) << nl;
+    }
+
 
     Info << "---\nEnd\n" << endl;
 

src/OpenFOAM/primitives/nil/nil.H

@@ -1,97 +0,0 @@
-/*---------------------------------------------------------------------------*\
-  =========                 |
-  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
-   \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2011 OpenFOAM Foundation
-     \\/     M anipulation  |
--------------------------------------------------------------------------------
-License
-    This file is part of OpenFOAM.
-
-    OpenFOAM is free software: you can redistribute it and/or modify it
-    under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 3 of the License, or
-    (at your option) any later version.
-
-    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
-    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
-    for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
-
-Class
-    Foam::nil
-
-Description
-    A zero-sized class without any storage. Used, for example, in HashSet.
-
-Note
-    A zero-sized class actually does still require at least 1 byte storage.
-
-\*---------------------------------------------------------------------------*/
-
-#ifndef nil_H
-#define nil_H
-
-// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
-
-namespace Foam
-{
-
-// Forward declaration of classes
-class Istream;
-class Ostream;
-
-// Forward declaration of friend functions and operators
-
-class nil;
-
-Istream& operator>>(Istream&, nil&);
-Ostream& operator<<(Ostream&, const nil&);
-
-
-/*---------------------------------------------------------------------------*\
-                             Class nil Declaration
-\*---------------------------------------------------------------------------*/
-
-class nil
-{
-
-public:
-
-    // Constructors
-
-        //- Construct null
-        nil()
-        {}
-
-        //- Construct from Istream
-        nil(Istream&)
-        {}
-
-
-    // IOstream Operators
-
-        friend Istream& operator>>(Istream& is, nil&)
-        {
-            return is;
-        }
-
-        friend Ostream& operator<<(Ostream& os, const nil&)
-        {
-            return os;
-        }
-};
-
-
-// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
-
-} // End namespace Foam
-
-// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
-
-#endif
-
-// ************************************************************************* //

src/OpenFOAM/primitives/nullObject/nullObject.H

@@ -22,12 +22,13 @@ License
     along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 
 Class
-    Foam::nullObject
+    Foam::NullObject
 
 Description
     Singleton null-object class and instance.
-    It occupies enough space to reinterpret its content as a class with
-    a null pointer for its content.
+    Its contents occupy just enough space to also be reinterpreted
+    as another class with a null pointer or zero long for its first
+    member.
 
 SourceFiles
     nullObjectI.H
@@ -43,8 +44,14 @@ SourceFiles
 namespace Foam
 {
 
+// Forward declarations
+class Istream;
+class Ostream;
+
+class NullObject;
+
 /*---------------------------------------------------------------------------*\
-                         Class nullObject Declaration
+                         Class NullObject Declaration
 \*---------------------------------------------------------------------------*/
 
 class NullObject
@@ -55,12 +62,12 @@ class NullObject
     {
         void* ptr;
         unsigned long val;
-    } null;
+    } content;
 
-    //- Private constructor
+    //- Private constructor for singleton only
     NullObject()
     :
-        null{nullptr}
+        content{nullptr}
     {}
 
     //- Disallow default bitwise copy construct
@@ -70,23 +77,44 @@ class NullObject
     void operator=(const NullObject&) = delete;
 
 public:
-    //- The unique null object
-    static const NullObject nullObject;
 
-    //- A nullptr pointer content
-    inline const void* pointer() const
-    {
-        return null.ptr;
-    }
+    // Static Data
 
-    //- A zero value content
-    inline unsigned long value() const
-    {
-        return null.val;
-    }
+        //- A unique null object
+        static const NullObject nullObject;
+
+
+    // Member Functions
+
+        //- A nullptr pointer content
+        inline const void* pointer() const
+        {
+            return content.ptr;
+        }
+
+        //- Zero valued integer content
+        inline unsigned long value() const
+        {
+            return content.val;
+        }
 };
 
 
+// IOstream Operators
+
+//- Read from Istream consumes no content.
+inline Istream& operator>>(Istream& is, NullObject&)
+{
+    return is;
+}
+
+//- Write to Ostream emits no content.
+inline Ostream& operator<<(Ostream& os, const NullObject&)
+{
+    return os;
+}
+
+
 //- Pointer to the unique nullObject
 extern const NullObject* nullObjectPtr;
 

src/OpenFOAM/primitives/one/one.H

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-     \\/     M anipulation  |
+     \\/     M anipulation  | Copyright (C) 2017 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -25,9 +25,8 @@ Class
     Foam::one
 
 Description
-    A class representing the concept of 1 (scalar(1.0)) used to avoid
-    unnecessary manipulations for objects which are known to be one at
-    compile-time.
+    A class representing the concept of 1 (or 1.0) used to avoid unnecessary
+    manipulations for objects that are known to be one at compile-time.
 
 SourceFiles
     oneI.H
@@ -44,6 +43,11 @@ SourceFiles
 namespace Foam
 {
 
+// Forward declaration of classes, friend functions and operators
+class Istream;
+class Ostream;
+class one;
+
 /*---------------------------------------------------------------------------*\
                            Class one Declaration
 \*---------------------------------------------------------------------------*/
@@ -51,15 +55,22 @@ namespace Foam
 class one
 {
 public:
-
     typedef one value_type;
 
+    // Forward declaration
+    class null;
+
+
     // Constructors
 
-        //- Construct null
+        //- Null constructible
         one()
         {}
 
+        //- Construct null from Istream. Consumes no content.
+        explicit one(Istream&)
+        {}
+
 
     // Member operators
 
@@ -83,6 +94,43 @@ public:
 };
 
 
+/*---------------------------------------------------------------------------*\
+                          Class one::null Declaration
+\*---------------------------------------------------------------------------*/
+
+//- A one class with a null output adapter.
+class one::null
+:
+    public one
+{
+public:
+    typedef null value_type;
+
+    //- Null constructible
+    null()
+    {}
+
+    //- Construct null from Istream without consuming any content.
+    explicit null(Istream&)
+    {}
+};
+
+
+// IOstream Operators
+
+//- Read from Istream consumes no content.
+inline Istream& operator>>(Istream& is, one&)
+{
+    return is;
+}
+
+//- Write to Ostream emits no content.
+inline Ostream& operator<<(Ostream& os, const one::null&)
+{
+    return os;
+}
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 } // End namespace Foam

src/OpenFOAM/primitives/strings/wordRes/wordReListMatcher.H

@@ -39,13 +39,11 @@ Description
 
 namespace Foam
 {
-
      typedef wordRes wordReListMatcher;
+}
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-} // End namespace Foam
-
 #endif
 
 // ************************************************************************* //

src/OpenFOAM/primitives/zero/nil.H

@@ -0,0 +1,24 @@
+/*---------------------------------------------------------------------------*\
+Compatibility include
+
+Typedef
+    Foam::nil
+
+Description
+    The older name for Foam::zero::null.
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef nil_H
+#define nil_H
+
+#include "zero.H"
+
+namespace Foam
+{
+    typedef zero::null nil;
+}
+
+#endif
+
+// ************************************************************************* //

src/OpenFOAM/primitives/zero/zero.H

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-     \\/     M anipulation  |
+     \\/     M anipulation  | Copyright (C) 2017 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -43,6 +43,12 @@ SourceFiles
 namespace Foam
 {
 
+// Forward declarations
+class Istream;
+class Ostream;
+
+class zero;
+
 /*---------------------------------------------------------------------------*\
                            Class zero Declaration
 \*---------------------------------------------------------------------------*/
@@ -50,15 +56,22 @@ namespace Foam
 class zero
 {
 public:
-
     typedef zero value_type;
 
+    // Forward declaration
+    class null;
+
+
     // Constructors
 
-        //- Construct null
+        //- Null constructible
         zero()
         {}
 
+        //- Construct null from Istream. Consumes no content.
+        explicit zero(Istream&)
+        {}
+
 
     // Member operators
 
@@ -85,9 +98,47 @@ public:
         {
             return 0;
         }
+
 };
 
 
+/*---------------------------------------------------------------------------*\
+                         Class zero::null Declaration
+\*---------------------------------------------------------------------------*/
+
+//- A zero class with a null output adapter.
+class zero::null
+:
+    public zero
+{
+public:
+    typedef null value_type;
+
+    //- Null constructible
+    null()
+    {}
+
+    //- Construct null from Istream without consuming any content.
+    explicit null(Istream&)
+    {}
+};
+
+
+// IOstream Operators
+
+//- Read from Istream consumes no content.
+inline Istream& operator>>(Istream& is, zero&)
+{
+    return is;
+}
+
+//- Write to Ostream emits no content.
+inline Ostream& operator<<(Ostream& os, const zero::null&)
+{
+    return os;
+}
+
+
 // Global zero
 static const zero Zero;